Method of administering phospholipid dispersions

ABSTRACT

A method of administering a surfactant dispersion to the lungs of a patient in need of such treatment is disclosed. The method comprises heating the dispersion and nebulizing the heated dispersion to produce respirable surfactant particles. The respirable surfactant particles delivered to the lungs of the patient. By heating the dispersion the amount of phospholipid delivered to the lungs of the patient is increased. 
     The dispersion is comprised of a phospholipid dispersed in an aqueous carrier. In a particular embodiment of the invention, the phospholipid is preferably dipalmitoylphosphatidylcholine (DPPC) included in an amount from about 8 to 50 milligrams per milliliter of aqueous carrier, and the dispersion is preferably heated to a temperature between about 25° C. and 75° C.

FIELD OF THE INVENTION

The present invention concerns methods for the administration ofaerosolized surfactant formulations to the lungs of a patient.

BACKGROUND OF THE INVENTION

Respiratory distress syndrome (RDS), also termed hyaline membranedisease, is the leading cause of death and disability among prematureinfants. Of the 230,000 to 250,000 infants born prematurely each year inthe United States, 40,000 to 50,000 develop RDS; and of those whodevelop this disease, 5,000 to 8,000 die. See generally R. Perelman andP. Farrell, Pediatrics 70, 570 (1982); D. Vidyasagar, in HyalineMembrane Disease: Pathogenesis and Pathophysiology, 98 (L. Stern Ed.1984). In addition, RDS can occur in children, adolescents, and adultsas a result of trauma or other injury to the lungs. 150,000 cases ofadult respiratory distress syndrome (ARDS) are reported annually, with60-80% mortality. See American Lung Program, Respiratory Diseases, TaskForce Report on Problems, Research Approaches, and Needs, National Heartand Lung Institute, DHEW Publn. (NIH) 73-432: 165-80 (1972).

RDS is caused by a primary deficiency in lung surfactant, a materialordinarily secreted onto the surface of lung alveoli. ARDS consists of asecondary deficiency in lung surfactant due to surfactant inhibitionand/or decreased secretion. In the absence of surfactant, the alveolitend to collapse during exhalation. Collapse can be avoided bymechanically ventilating the lungs. A problem with mechanicalventilation, however, is that it can cause damage to the lungs becauseof high oxygen concentrations and positive pressures.

A number of groups have sought to develop surfactant formulations whichcan be used to treat or prevent RDS and ARDS. Both human and bovinenatural surfactants have been administered into the airways of humansubjects. See, e.g., J. Horbar et al., N. Eng. J. Med. 320, 959 (1989);R. Soll et al., Pediatric Res. 23, 425A (1988). Problems with suchnatural surfactants are, however, potential contamination withmicroorganisms and potential sensitization of the patient to proteinstherein. Accordingly, completely synthetic surfactants have beendeveloped. See, e.g., U.S. Pat. No. 4,826,821 to Clements; U.S. Pat. No.4,312,860 to Clements.

While the development of surfactant formulations have provided analternative to mechanical ventilation alone, clinicians are now facedwith the difficult problem of how to quickly and efficaciouslyadminister these formulations to the lungs of patients. U.S. Pat. No.4,832,012 to Raabe and Lee discloses a nebulizing apparatus which may beused to deliver drug-containing liquids to the lungs of patients in theform of an aerosol. It is suggested that the liquid can be heated orcooled prior to nebulization (column 4, lines 47-48). Raabe and Lee donot address the problems involved in administering surfactantformulations to the lungs of a patient. Such formulations aredispersions of lipids in an aqueous carrier solution, rather than singlephase solutions.

In view of the foregoing, an object of the present invention is toprovide a means for administering surfactant formulations to the lungsof patients in the form of an aerosol.

SUMMARY OF THE INVENTION

The present invention provides a method of administering a surfactantdispersion to the lungs of a patient in need of such treatment. Themethod comprises heating the dispersion to a temperature between about25° C. and 90° C. The dispersion is comprised of a phospholipiddispersed in an aqueous carrier. The phospholipid is included in anamount from about 10 to 90 milligrams per milliliter of aqueous carrier.The dispersion is nebulized to produce respirable surfactant particles,and the respirable surfactant particles delivered to the lungs of thepatient. By heating the dispersion prior to nebulization, the amount ofphospholipid delivered to the lungs of the patient is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows milligrams (mg) of dipalmitoylphosphatidylcholine (DPPC)collected over six hours from a nebulized 1× surfactant formulationmaintained at temperatures ranging from 2° Centigrade to 37° Centigrade.

FIG. 2 shows mg of DPPC collected over a six hour period from anebulized 3× surfactant formulation maintained at temperatures rangingfrom 2° C. to 37° C.

FIG. 3 shows mg of DPPC collected over a six hour period from anebulized 6× surfactant formulation maintained at temperatures rangingfrom 2° C. to 37° C.

FIG. 4 shows total mg of DPPC collected from a nebulized 1× surfactantformulation maintained at temperatures ranging from 2° C. to 60° C.

FIG. 5 shows total mg of DPPC collected from a nebulized 3× surfactantformulation maintained at temperatures ranging from 2° C. to 60° C.

FIG. 6 shows total mg of DPPC collected from a nebulized 6× surfactantformulation maintained at temperatures ranging from 2° C. to 60° C.

DETAILED DESCRIPTION OF THE INVENTION

Surfactant formulations used in practicing the present invention may beof any type useful for the treatment of RDS or ARDS, whether of natural(i.e., human, bovine), see, e.g., J. Horbar et al., N. Eng. J. Med. 320,959 (1989); R. Soll et al., Pediatric Res. 23, 425A (1988), recombinant,or synthetic origin, or combinations thereof. See, e.g., Y. Tanaka etal., J. Lipid Res. 27, No. 2, 475 (1986), T. Fujiwara et al., Lancet 1,55 (Jan. 12, 1980) (cow-lung extract fortified withdipalmitoylphosphatidylcholine); U.S. Pat. No. 4,912,038 to Schilling etal. (recombinant DNA sequences encoding alveolar surfactant proteins).Particularly preferred for practicing the present invention is syntheticsurfactant of the type described in U.S. Pat. No. 4,826,821 to Clements(Applicants specifically intend that the disclosure of all patentreferences cited herein be incorporated herein by reference). Alsouseful for practicing the present invention is synthetic surfactant ofthe type described in U.S. Pat. No. 4,312,860 to Clements. Anothersurfactant formulation is commercially available from Ross Laboratoriesas SURVANTA®, which is a natural bovine lung extract containingphospholipids, neutral lipids, fatty acids, and surfactant-associatedproteins to which dipalmitoylphosphatidylcholine, palmitic acid, andtripalmitin are added to standardize the composition and to mimicsurface tension lowering properties of natural lung surfactant. Thesurfactant formulation may be provided as a sterile lyophylized powder,which is reconstituted prior to use, or as a ready-to-use liquid.

In general, all surfactant formulations containdipalmitoylphosphatidylcholine (DPPC; also called "ColfoscerilPalmitate") as a phospholipid in an aqueous carrier, either alone or incombination with other phospholipids such as1-palmitoyl-2-oleoylphosphatidylglycerol, dimyristoylphosphatidylcholine, distearoyl phosphatidylcholine, dimyristoylphosphatidylethanolamine, dilauroyl phosphatidylethanolamine, dimethyldipalmitoyl phosphatidylcholine, methyl dipalmitoyl phosphatidylcholine,dipalmitoyl phosphatidylglycerol, phosphatidylcholine, dipalmitoylphosphatidyl ethanolamine, dilauroyl phosphatidylcholine, dioleoylphosphatidylcholine, and dibehenoyl phosphatidylcholine. Typically, DPPCis included in an amount from 10 to 90 mg/mL in a surfactant formulationto be nebulized and administered to the lungs.

Surfactant formulations typically have a surface tension less than 15dynes per centimeter. Lower surface tensions (e.g., less than about 10dynes per centimeter) tend to be preferred, with the surfactantformulations described herein being capable of providing surfacetensions down to about 1 to 2 dynes per centimeter or less.

Surfactant formulations preferably include a spreading agent such as afatty alcohol or a lung surfactant protein in an amount effective tospread the surfactant formulation on the surface of lung alveoli. In aparticularly preferred embodiment of the present invention the spreadingagent is cetyl alcohol (also called hexadecanol).

The aqueous phase of the surfactant formulation is preferably a salinesolution (e.g., a sodium chloride solution), so as to not be undulyirritating to lung surfaces. Sodium chloride solutions may be normalsaline solutions (i.e., about 0.9% NaCl), or are more preferablyslightly hypotonic (e.g., about 0.4% to about 0.9% NaCl, more preferablyabout 0.4% to about 0.8% NaCl, and most preferably 0.54% NaCl).

Suitable surfactant formulations include those containing a lungsurfactant protein as the spreading agent, as noted above. An example ofsuch a formulation is prepared by combining a surfactant apoprotein suchas described in U.S. Pat. No. 4,912,038 with a mixture of lipids, wherethe mixture of lipids includes DPPC,1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), and palmitic acid(PA), with the ratio of DPPC to POPG being from 50:50 to 90:10; with theratio of (DPPC+POPG) to surfactant protein being from 50:1 to 5:1; andwith the ratio of PA to (DPPC+POPG) being from 0 to 0.2. Otherunsaturated acidic lipids than POPG may be substituted for POPG. In aparticularly preferred embodiment of this type of formulation, the ratioof DPPC to POPG to PA is 7:3:1, with a final phospholipid concentrationof 3 times the amount of lipid, with calcium incorporated atapproximately 0.01 mg/mL to 10 mg/mL Ca²⁺. See, e.g., PCT ApplicationPublication No. WO 91/00871 of Genentech Inc. and CaliforniaBiotechnology Inc. (Published Jan. 24, 1991).

The dispersion is preferably heated to a temperature between about 25°C. and 75° C., and the phospholipid is preferablydipalmitoylphosphatidylcholine (DPPC) included in an amount from about 8to 50 milligrams per milliliter of aqueous carrier. "Heated"temperatures referred to herein are temperatures of the heating means(i.e., the heating block); the liquid surfactant formulation itselfreaches a temperature somewhat lower than the heating means due to thecooling effect of nebulization). Various combinations of heating andphospholipid concentration may be employed in practicing the presentinvention, with the following embodiments employing DPPC beingillustrative, and with the embodiment set forth in paragraph 7 belowbeing particularly preferred:

(1) A method wherein the dispersion is heated to a temperature of about25° C. to 55° C. and the DPPC is included in the aqueous carrier in anamount from about 30 to 50 milligrams per milliliter (mg/mL). Morepreferably, the dispersion is heated to a temperature of about 35° C. to45° C. and the DPPC is included in an amount from about 35 to 45 mg/mL.Most preferably, the dispersion is heated to a temperature of about 37°C. and the DPPC is included in an amount of about 40.5 mg/mL.

(2) A method wherein the dispersion is heated to a temperature of about45° C. to 75° C., and the DPPC is included in the aqueous carrier in anamount from about 70 to 90 mg/mL. More preferably, the dispersion isheated to a temperature of about 55° C. to 65° C. and the DPPC isincluded in an amount from about 75 to 85 mg/mL. Most preferably, thedispersion is heated to a temperature of about 60° C. and the DPPC isincluded in an amount of about 81 mg/mL.

(3) A method wherein the dispersion is heated to a temperature of about25° C. to 55° C. and the DPPC is included in the aqueous carrier in anamount from about 70 to 90 mg/mL. More preferably, the dispersion isheated to a temperature of about 35° C. to 45° C. and the DPPC isincluded in an amount from about 75 to 85 mg/mL. Most preferably, thedispersion is heated to a temperature of about 37° C. and the DPPC isincluded in an amount of about 81 mg/mL.

(4) A method wherein the dispersion is heated to a temperature of about45° C. to 75° C. and the DPPC is included in the aqueous carrier in anamount from about 30 to 50 mg/mL. More preferably, the dispersion isheated to a temperature of about 55° C. to 65° C. and the DPPC isincluded in an amount from about 35 to 45 mg/mL. Most preferably, thedispersion is heated to a temperature of about 60° C. and the DPPC isincluded in an amount of about 40.5 mg/mL.

(5) A method wherein the dispersion is heated to a temperature of about25° C. to 55° C. and the DPPC is included in the aqueous carrier in anamount from about 5 to 24 mg/mL. More preferably, the dispersion isheated to a temperature of about 35° C. to 45° C. and the DPPC isincluded in an amount from about 8 to 20 mg/mL. Most preferably, thedispersion is heated to a temperature of about 37° C. and the DPPC isincluded in an amount of about 13.5 mg/mL.

(6) A method wherein the dispersion is heated to a temperature of about45° C. to 75° C. and the DPPC is included in the aqueous carrier in anamount from about 5 to 24 mg/mL. More preferably, the dispersion isheated to a temperature of about 55° C. to 65° C. and the DPPC isincluded in an amount from about 8 to 20 mg/mL. Most preferably, thedispersion is heated to a temperature of about 60° C. and the DPPC isincluded in an amount of about 13.5 mg/mL.

(7) A method wherein the dispersion is heated to a temperature of about45° C. to 75° C. and the DPPC is included in the aqueous carrier in anamount from about 5 to 24 milligrams per milliliter (mg/mL). Morepreferably, the dispersion is heated to a temperature of about 45° C. to55° C., and the DPPC is included in an amount of from about 8 to 20mg/mL. Most preferably, the dispersion is heated to a temperature ofabout 50° C. and the DPPC is included in an amount of about 13.5 mg/mL.

(8) A method wherein the dispersion is heated to a temperature of about45° C. to 75° C. and the DPPC is included in the aqueous carrier in anamount from about 30 to 50 mg/mL. More preferably, the dispersion isheated to a temperature of about 45° C. to 55° C., and the DPPC isincluded in an amount of from about 35 to 45 mg/mL. Most preferably, thedispersion is heated to a temperature of about 50° C. and the DPPC isincluded in an amount of about 40.5 mg/mL.

(9) A method wherein the dispersion is heated to a temperature of about45° C. to 75° C., and the DPPC is included in the aqueous carrier in anamount from about 70 to 90 mg/mL. More preferably, the dispersion isheated to a temperature of about 45° C. to 55° C., and the DPPC isincluded in an amount of from about 75 to 85 mg/mL. Most preferably, thedispersion is heated to a temperature of about 50° C. and the DPPC isincluded in an amount of about 81 mg/mL.

In general, the dispersion is heated to a temperature of at least aboutthe transition temperature of the phospholipid. Note that nebulizationof the surfactant formulation causes the temperature of that formulationto drop, so heating the formulation will be required to maintain thetemperature of the surfactant formulation even at room temperatureduring continuous nebulization.

Respirable surfactant particles may be delivered to a patient by anysuitable means, including spontaneous inhalation and mechanicalventilation. In spontaneous inhalation, the patient inhales thesurfactant particles. Numerous different aerosol inhalers are known. Theterm "ventilation" herein refers to the process of cyclically forcingoxygen-rich air into, and permitting oxygen-depleted air to escape from,at least one lung of a patient to assist the breathing of the patient orto breath for the patient when the patient would not otherwise breath onits own. Ventilation may be of either or both lungs of a patient,depending on whether any one lung is blocked, collapsed, or otherwiseinoperable. Numerous types of ventilating apparatus are known. Whenrespirable particles are to be administered to a particles byventilation, the respirable particles are typically generated by meansof a nebulizer, with the nebulizer output combined with or delivered tothe ventilator output for ultimate delivery to the patient. Thenebulizer can load the ventilator during the inhalation phase orexhalation phase of the ventilator cycle.

Any nebulizing apparatus capable of forming respirable particles (e.g,particles from 1 to 10 microns volume meadian diameter in size) from asurfactant formulation as described above may be employed in practicingthe present invention, including both jet nebulizers and ultrasonicnebulizers. Those skilled in the art will appreciate that the aerosolproduced by the nebulizing apparatus may contain larger particles whichare not respirable, so long as a sufficient quantity of respirableparticles are included in the aerosol to accomplish the intendedpurpose. An example jet nebulizer is described in U.S. Pat. No.4,832,012. Example ultrasonic nebulizers include the Porta-Sonic™ andthe Pulmo-Sonic™ nebulizers produced by The DeVilbiss Co., Somerset,Pa., USA.

The present invention is explained in greater detail in the examples setforth below. In the examples, "cc" means cubic centimeter, "g" meansgrams, "mg" means milligrams, "mL" means milliliter, "psi" means poundsper square inch, "mOsm⃡ means milliosmoles, "N" means normal, "L" meansliter, "min" means minutes, "hr" means hour, percentages are given on aby-weight basis, "Amb" means ambient, and temperatures are given indegrees Centigrade unless otherwise indicated.

EXAMPLE 1 Preparation of Surfactant Formulation

25 cc of sterile, pyrogen-free water is taken up in a sterile disposablesyringe and injected into a sterile, evacuated, 50 cc vial containing alyophilized powder of 2.025 g dipalmitoylphosphatidylcholine (DPPC), 225mg hexadecanol, 150 mg tyloxapol, and 876.6 mg NaCl. This mixture isknown. See U.S. Pat. No. 4,826,821 to Clements. The water and powder arevigorously mixed by inverting the vial and repeatedly withdrawing themixture into the syringe and releasing the plunger of the syringe. Theresult is approximately 25 cc of surfactant formulation, which is asuspension rather than a solution. The formulation is placed in anebulizer well and diluted as needed with 125 mL of sterile pyrogen freewater. The resulting surfactant formulation is 0.1N with respect toNaCl, has an osmolality of 190 mOsm/1, and contains 13.5 mg/cc of DPPC,1.5 mg/cc of hexadecanol, and 1 mg/cc of tyloxapol. This formulation isreferred to below as a 1× surfactant formulation. A 3× and 6 ×surfactant formulation is prepared in essentially the same manner,except that the DPPC, hexadecanol, and tyloxapol are increased three andsix times by weight, respectively. NaCl is maintained at approximately a0.1 N concentration in the 3× and 6× formulations.

EXAMPLE 2 Test Apparatus

A test apparatus was assembled from a SERVO 900C ventilator(Siemens-Elema AB, Sweden) and a VISAN™ nebulizer unit (Vortran MedicalTechnology ,Inc., Sacramento, Calif.). Compressed air (50 psi) wassupplied to an oxygen/air blender and used to supply gas to both theventilator and the nebulizer, with the nebulizer gas supply passingthrough a separate nebulizer flowmeter. The nebulizer control unit waselectrically connected to the electrical signal source of the respiratorwhich controls the inhalation phase of the breathing cycle so thatnebulized surfactant was delivered intermittently, during the inhalationphase of the ventilator respiratory function. The ventilator andnebulizer output were each connected to a patient Y tube, which was inturn connected to a 7 foot section of TYGON™ tubing (R-3603, 7/8" i.d.)coiled inside of a 4 liter Ehrlenmeyer filter flask. The output of thefilter flask was connected to a second 7 foot section of TYGON™ tubingwhich was coiled inside a second 4 liter Ehrlenmeyer filter flask. Thecoiled tubing served as artificial lungs to collect the nebulizedsurfactant formulation. The filter flasks were sealed with latex glovesand placed in methanol/dry ice baths prior to each experiment. The bathtemperature was regulated during the experiment to avoid collection tubeocclusion caused by freezing.

The ventilator and nebulizer unit were set to deliver a combined totalinspiratory tidal volume (V_(t)) of 750 mL/breath. Initial tidal volumeswere checked by installing a rubber "lung" at the patient Y tube andobserving the appropriate ventilator gauges. Ventilator mean airwaypressure (cm water) was monitored and recorded initially and at eachsampling time to determine the back pressure on the system. Instrumentsettings for the ventilator and nebulizer unit were as follows: Theventilator was set to a Working pressure of 70 cm water; a breathingrate (f) of 20 breaths/min; an inhalation fraction (P_(i)) of 25%; andan Inspiratory Minute Volume (MV) of 7.5 L/min. The nebulizer was set toa working pressure of 50 psi; a flow rate (from flowmeter) of 30 L/min;and a flow rate (from nebulizer) of 500 mL/sec (2 nebulizer jets open).

EXAMPLE 3 Nebulization of Surfactant Formulations at Ambient and IceBath Temperatures

A total of 18 experiments were performed utilizing the parameters listedin Table 1 (subsequent Tables refer to Table 1 for the definition ofexperiments).

                  TABLE 1                                                         ______________________________________                                        Experimental Parameters                                                                                       Nebulizer                                     Experiment                                                                            Surfactant  Delivery Tube                                                                             Bath                                          Number  Preparation Length (feet)                                                                             Temperature                                   ______________________________________                                        A       1X          4           ice                                           B       1X          0.5         ice                                           C       1X          2           ice                                           D       3X          4           ice                                           E       3X          0.5         ice                                           F       3X          2           ice                                           G       6X          4           ice                                           H       6X          0.5         ice                                           I       6X          2           ice                                           J       1X          4           ambient                                       K       1X          0.5         ambient                                       L       1X          2           ambient                                       M       3X          4           ambient                                       N       3X          0.5         ambient                                       O       3X          2           ambient                                       P       6X          4           ambient                                       Q       6X          0.5         ambient                                       R       6X          2           ambient                                       ______________________________________                                    

Variables included the surfactant formulation concentration (1×, 3×,6×), the nebulizer--Y delivery tube length, the nebulization bathtemperature (ice water temperature at about 2° C., or ambienttemperature at about 22° C.), and nebulization time. Samples taken fromthe nebulizer and collection flasks were removed at 2, 4, and 6 hoursafter beginning nebulization. Nebulizers were weighed initially and uponcompletion of the experiment to determine the total amount of surfactantnebulized by weight. The collection flasks were removed from theventilator circuit at predetermined sampling times, allowed toequilibrate to room temperature, and subsequent sets of cooled flasksinstalled immediately following removal. The total volume of collectedmaterial was measured and then combined with a 150-mL distilled waterrinse of the flasks and Tygon tubing. The collected and rinse fractionswere combined, mixed, and equal portions aliquoted into four 50-mL glassvials.

Nebulizer samples were obtained by removing 10-mL fraction from thenebulizer at each sampling time. Three 3-mL portions of the nebulizerfraction were then transferred to 10-mL glass vials. Both the collectedand nebulizer samples were lyophilized using a Virtis freeze dryer for3-4 days.

The Tygon tubing and flasks were thoroughly rinsed with hot anddistilled water and allowed to dry after each sampling period. Thenebulizer and ventilator tubing were replaced after each experiment.

The lyophilized samples were dissolved in either methanol or chloroform,diluted appropriately according to their initial concentration, andtested (a) for DPPC concentration by HPLC analysis, (b) for Tyloxapolconcentration by UV determination, and (c) for cetyl alcoholconcentration by GC analysis.

The relative weight loss from nebulization (which can be related toefficiency) determinations from the initial and final weights arecontained in Table 2. Note that the weight loss numbers include the 30mL of liquid taken from the nebulizer for sampling purposes. Althoughthis fraction was not aerosolized, the amount removed was constant foreach experiment. The weight loss determinations can therefore be usedfor comparison for the experimental variables.

                  TABLE 2                                                         ______________________________________                                        Relative Weight Loss From Nebulization                                        Experiment      % Weight                                                      Number          Loss      Mean                                                ______________________________________                                        A               60.1      61.1                                                B               62.9                                                          C               60.2                                                          D               58.2      51.5                                                E               48.3                                                          F               48.1                                                          G               61.6      55.4                                                H               49.1                                                          I               55.4                                                          J               73.0      73.1                                                K               80.9                                                          L               65.3                                                          M               61.1      57.5                                                N               52.7                                                          O               58.6                                                          P               62.7      61.4                                                Q               56.4                                                          R               65.0                                                          ______________________________________                                    

Table 3 lists collection flask volumes recovered from the experiments.The experiments are grouped by the surfactant formulation reconstitutionstrength (1×, 3×, or 6×). There were no trends in the data to suggestdelivery tube length had any significant effect on the volume or mass ofsurfactant formulation collected. There were also no significantdifferences in results determined for the 2, 4, and 6 hour collectiontimes. Therefore, to simplify examination of the data, averages ofvalues for collected tube lengths and total amount collected arepresented for 1×, 3×, and 6× concentrations at ice or ambienttemperature. Collected fraction total mass determinations are presentedin Tables 4-7.

                  TABLE 3                                                         ______________________________________                                        Collected Volumes (mL)                                                        Experiment  2      4          6    Total mL                                   Number      Hour   Hour       Hour Collected                                  ______________________________________                                         A*         19     22         17   58                                         B           14     17         12   43                                         C           17     17         15   49                                         D           12     21         20   53                                         E           14     19          9   42                                         F           17     14         14   45                                          G*         19     19         21   59                                          H*         18     10          5   33                                         I           19     15         14   48                                         J           20     10         25   55                                          K*         21     19         17   57                                         L           18     16         17   51                                         M           18     26         17   61                                         N           22     27         19   68                                         O           23     22         14   59                                         P           18     20         18   56                                         Q           19     20         17   56                                         R           25     19         20   64                                         ______________________________________                                         *Mean of 2 Experiments                                                   

                  TABLE 4                                                         ______________________________________                                        Collected Fractions - DPPC Determinations                                                        Initial      Mean  Mean                                                       Nebulizer    Total Total                                   Surfactant                                                                             Nebulizer Concentration                                                                              Mass  Volume                                  Formulation                                                                            Bath      mg/mL        (mg)  (mL)                                    ______________________________________                                        1X       Ice       13.5         128.1 50.0                                    3X       Ice       40.5         412.8 46.7                                    6X       Ice       81.0         894.9 46.7                                    1X       Amb       13.5         217.7 54.3                                    3X       Amb       40.5         665.6 62.7                                    6X       Amb       81.0         1341.5                                                                              58.7                                    ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        Collected Fractions - Tyloxapol Determinations                                                   Initial      Mean  Mean                                                       Nebulizer    Total Total                                   Surfactant                                                                             Nebulizer Concentration                                                                              Mass  Volume                                  Formulation                                                                            Bath      mg/mL        (mL)  (mL)                                    ______________________________________                                        1X       Ice       1.0          19.4  50.0                                    3X       Ice       3.0          51.2  46.7                                    6X       Ice       6.0          91.2  46.7                                    1X       Amb       1.0          27.5  54.3                                    3X       Amb       3.0          81.5  62.7                                    6X       Amb       6.0          138.1 58.7                                    ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Collected Fractions - Cety Alcohol Determinations                                                Initial      Mean  Mean                                                       Nebulizer    Total Total                                   Surfactant                                                                             Nebulizer Concentration                                                                              Mass  Volume                                  Formulation                                                                            Bath      mg/mL        (mg)  (mL)                                    ______________________________________                                        1X       Ice       1.5          12.1  50.0                                    3X       Ice       4.5          40.4  46.7                                    6X       Ice       9.0          77.3  46.7                                    1X       Amb       1.5          21.1  54.3                                    3X       Amb       4.5          62.7  62.7                                    6X       Amb       9.0          144.4 58.7                                    ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        Collected Fractions - Sodium Chloride Determinations                                             Initial      Mean  Mean                                                       Nebulizer    Total Total                                   Surfactant                                                                             Nebulizer Concentration                                                                              Mass  Volume                                  Formulation                                                                            Bath      mg/mL        (mg)  (mL)                                    ______________________________________                                        1X       Ice       5.8           61.3 50.0                                    3X       Ice       5.2           67.6 46.7                                    6X       Ice       5.8           77.1 46.7                                    1X       Amb       5.8          104.7 54.3                                    3X       Amb       5.2          100.3 62.7                                    6X       Amb       5.8          117.6 58.7                                    ______________________________________                                    

Analysis of Tables 2-7 above indicate that nebulization efficiency byweight, collected volumes, and collected mass determinations are higherusing ambient nebulizer baths (Experiments J-R) as compared to the icewater nebulizer baths (Experiments A-I).

EXAMPLE 4 Nebulization of Surfactant Formulations at 37 DegreesCentigrade

This experiment was undertaken to investigate surfactant nebulization at37° C. The apparatus employed was essentially the same as described inExample 2 above, except that a Brinkman IC-2 immersion heater/circulatorwas used with the nebulizer bath. Duplicate experiments were performedat 37° for 1×, 3×, and 6× surfactant formulation concentrations.Experimental conditions were essentially the same as described inExample 2 above, except that (a) a 4 foot delivery tube length wasutilized for all the experiments; the nebulizer bath temperature wasmaintained at 37° C.; (c) the nebulizer was initially filled with 200mLof the respective surfactant formulation (as opposed to 150mL in Example2); (d) an additional 50mL of the surfactant formulation was added tothe nebulizer after the 4 hour collection period for the 3× and 6×experiments; (e) rinse volumes for the collection vessels and Tygontubing were decreased to 50mL for each flask and tubing (compared to75mL in the previous study); and (f) testing of the collected+rinsefractions for DPPC was done directly on methanol dilutions of thesamples rather than after lyophylization. The increased initialnebulizer volume and the addition of 50mL of surfactant formulation at 4hours were implemented to maintain sufficient levels of thereconstituted drug in the nebulizer. Rinse volumes were decreased toconcentrate the surfactant formulation constituents in the rinse pluscollected sample fractions.

Summarized results are presented in Table 8 along with the valuespreviously obtained for analogous experiments (4 foot delivery tubes) atice and ambient temperatures in Example 3 above. Where experiments havebeen repeated, data has been pooled. Both collected volumes and totalDPPC mass were increased compared to the values obtained in the earlierice and ambient studies. FIGS. 1-3 illustrate the mean total mass ofDPPC recovered as a function of nebulizer bath temperature. Bathtemperature values used were ice (2° C.), ambient (22° C.), and heated(37° C.). The results indicate increased DPPC total mass was deliveredwith increased nebulizer bath temperatures.

                  TABLE 8                                                         ______________________________________                                        Collected Fractions - DPPC Determinations                                                        Initial      Mean  Mean                                                       Nebulizer    Total Total                                   Surfactant                                                                             Nebulizer Concentration                                                                              Mass  Volume                                  Formulation                                                                            Bath      mg/mL        (mg)  (mL)                                    ______________________________________                                        1X       Ice       13.5         119   58                                      1X       Ambient   13.5         215   55                                      1X       37° C.                                                                           13.5         385   112                                     3X       Ice       40.5         604   53                                      3X       Ambient   40.5         719   61                                      3X       37° C.                                                                           40.5         1513  101                                     6X       Ice       81.0         1012  58                                      6X       Ambient   81.0         1274  56                                      6X       37° C.                                                                           81.0         988   80                                      ______________________________________                                    

EXAMPLE 5 Nebulization of Surfactant Formulations at 60 DegreesCentigrade

This experiment was undertaken to investigate the nebulization ofsurfactant formulation at 60° C. utilizing an apparatus and experimentalparameters as described in Example 4 above.

Summarized results are presented in Table 9 along with the valuespreviously obtained for analogous experiments (4 foot delivery tubes) atice, ambient and 37° temperatures as described in Examples 3 and 4above. Where experiments have been repeated, data has been pooled. FIGS.4-6 illustrate the mean total mass of DPPC recovered as a function ofnebulizer bath temperature. These data indicate the total DPPCdeliveries for the 1× and 6× reconstitutions were significantlyincreased as compared to the results obtained for analogous experimentsat ice, ambient, and 37° C. temperatures.

Surprisingly, the 3× surfactant formulation showed a decrease in DPPCdelivery at the 60° C. nebulization temperature as compared to thatfound in the 37° C. experiment. The mechanism producing this effect isunknown.

                  TABLE 9                                                         ______________________________________                                        Collected Fractions - DPPC Determinations                                                        Initial      Mean  Mean                                                       Nebulizer    Total Total                                   Surfactant                                                                             Nebulizer Concentration                                                                              Mass  Volume                                  Formulation                                                                            Bath      mg/mL        (mg)  (mL)                                    ______________________________________                                        1X       Ice       13.5         119   58                                      1X       Amb       13.5         215   55                                      1X       37° C.                                                                           13.5         385   112                                     1X       60°                                                                              13.5         562   115                                     3X       Ice       40.5         604   53                                      3X       Amb       40.5         719   61                                      3X       37° C.                                                                           40.5         1513  101                                     3X       60°                                                                              40.5         947   109                                     6X       Ice       81.0         1012  58                                      6X       Amb       81.0         1274  56                                      6X       37° C.                                                                           81.0         988   80                                      6X       60°                                                                              81.0         2045  79                                      ______________________________________                                    

The invention comprises any novel feature or combination of featuresdisclosed herein, including, but not limited to, the following.

We claim:
 1. A method of administering a surfactant dispersion to thelungs of a patient in need of such treatment, comprising:providing adispersion comprised of a phospholipid dispersed in an aqueous carrier;wherein said phospholipid is dipalmitoylphosphatidylcholine (DPPC); andwherein said DPPC is included in an amount from about 10 to 90milligrams per milliliter of aqueous carrier; then heating thedispersion to a temperature between about 25° C. and 90° C.; thennebulizing the dispersion to respirable surfactant particles; and thendelivering the respirable surfactant particles to the lungs of apatient.
 2. A method according to claim 1, wherein said dispersion isheated to a temperature of at least about the transition temperature ofsaid phospholipid.
 3. A method according to claim 1, wherein saiddispersion is heated to a temperature between about 25° C. and 75° C. 4.A method according to claim 1, wherein said DPPC is included in anamount from about 8 to 50 milligrams per milliliter of aqueous carrier.5. A method according to claim 1, wherein said surfactant dispersionfurther includes a spreading agent; and wherein said surfactantdispersion has a surface tension less than 15 dynes per centimeter.
 6. Amethod according to claim 5, wherein said spreading agent is a fattyalcohol.
 7. A method according to claim 5, wherein said spreading agentis cetyl alcohol.
 8. A method according to claim 5, wherein saidspreading agent is a lung surfactant protein.
 9. A method according toclaim 1, wherein said respirable particles are delivered by ventilation.10. A method according to claim 1, wherein said respirable particles arefrom about 1 to 10 microns in size.
 11. A method according to claim 1,wherein said nebulizing step is carried out with a jet nebulizer.
 12. Amethod according to claim 1, wherein said dispersion is heated to atemperature of about 25° C. to 55° C. and said DPPC is included in saidaqueous carrier in an amount from about 5 to 24 mg/mL.
 13. A methodaccording to claim 12, wherein said dispersion is heated to atemperature of about 35° C. to 45° C. and said DPPC is included in anamount from about 8 to 20 mg/mL.
 14. A method according to claim 13,wherein said dispersion is heated to a temperature of about 37° C. andsaid DPPC is included in an amount of about 13.5 mg/mL.
 15. A methodaccording to claim 1, wherein said dispersion is heated to a temperatureof about 45° C. to 75° C. and said DPPC is included in said aqueouscarrier in an amount from about 5 to 24 mg/mL.
 16. A method according toclaim 15, wherein said dispersion is heated to a temperature of about55° C. to 65° C. and said DPPC is included in an amount from about 8 to20 mg/mL.
 17. A method according to claim 16, wherein said dispersion isheated to a temperature of about 60° C. and said DPPC is included in anamount of about 13.5 mg/mL.
 18. A method of administering a surfactantdispersion to the lungs of a patient in need of such treatment,comprising:providing a dispersion comprised of a phospholipid dispersedin an aqueous carrier; wherein said phospholipid isdipalmitoylphosphatidylcholine (DPPC); wherein said DPPC is included inan amount from about 30 to 90 milligrams per milliliter of aqueouscarrier; wherein said surfactant dispersion further includes a spreadingagent; and wherein said surfactant dispersion has a surface tension lessthan 15 dynes per centimeter; then heating the dispersion to atemperature between about 25° C. and 75° C.; then nebulizing thedispersion to respirable surfactant particles; and then delivering therespirable surfactant particles to the lungs of a patient.
 19. A methodaccording to claim 18, wherein said dispersion is heated to atemperature of about 25° C. to 55° C., and wherein said DPPC is includedin said aqueous carrier in an amount from about 30 to 50 milligrams permilliliter.
 20. A method according to claim 19, wherein said dispersionis heated to a temperature of about 35° C. to 45° C., and wherein saidDPPC is included in said aqueous carrier in an amount from about 35 to45 milligrams per milliliter.
 21. A method according to claim 20,wherein said dispersion is heated to a temperature of about 37° C., andwherein said DPPC is included in said aqueous carrier in an amount ofabout 40.5 milligrams per milliliter.
 22. A method according to claim18, wherein said dispersion is heated to a temperature of about 45° C.to 75° C., and wherein said DPPC is included in said aqueous carrier inan amount from about 70 to 90 milligrams per milliliter.
 23. A methodaccording to claim 22, wherein said dispersion is heated to atemperature of about 55° C. to 65° C., and wherein said DPPC is includedin said aqueous carrier in an amount from about 75 to 85 milligrams permilliliter.
 24. A method according to claim 23, wherein said dispersionis heated to a temperature of about 60° C., and wherein said DPPC isincluded in said aqueous carrier in an amount of about 81 milligrams permilliliter.
 25. A method according to claim 18, wherein said dispersionis heated to a temperature of about 25° C. to 55° C., and wherein saidDPPC is included in said aqueous carrier in an amount from about 70 to90 milligrams per milliliter.
 26. A method according to claim 25,wherein said dispersion is heated to a temperature of about 35° C. to45° C., and wherein said DPPC is included in said aqueous carrier in anamount from about 75 to 85 milligrams per milliliter.
 27. A methodaccording to claim 26, wherein said dispersion is heated to atemperature of about 37° C., and wherein said DPPC is included in saidaqueous carrier in an amount of about 81 milligrams per milliliter. 28.A method according to claim 18, wherein said dispersion is heated to atemperature of about 45° C. to 75° C., and wherein said DPPC is includedin said aqueous carrier in an amount from about 30 to 50 milligrams permilliliter.
 29. A method according to claim 28, wherein said dispersionis heated to a temperature of about 55° C. to 65° C., and wherein saidDPPC is included in said aqueous carrier in an amount from about 35 to45 milligrams per milliliter.
 30. A method according to claim 29,wherein said dispersion is heated to a temperature of about 60° C., andwherein said DPPC is included in said aqueous carrier in an amount ofabout 40.5 milligrams per milliliter.
 31. A method according to claim18, wherein said spreading agent is a fatty alcohol.
 32. A methodaccording to claim 18, wherein said spreading agent is cetyl alcohol.33. A method according to claim 18, wherein said spreading agent is alung surfactant protein.
 34. A method according to claim 18, whereinsaid respirable particles are delivered by ventilation.
 35. A methodaccording to claim 18, wherein said respirable particles are from about1 to 10 microns in size.
 36. A method according to claim 18, whereinsaid nebulizing step is carried out with a jet nebulizer.